Description of the Prior Art
Currently, there are many applications in industry where particulate solids are used. Further, additional uses for particulate solids are regularly being found.
Chemical processing and steam generation are among the industries that have beneficially used particulate solids, both catalytic and inert, as means for accomplishing hydrocarbon cracking and heat transfer. Therein, very high temperatures (above 1500.degree. F.) and high mass flow of the particulate solids are experienced. Thus, problems result when flow regulation of the particulate solids is attemped by the use of mechanical valves. The high temperature environment and high mass flow cause deterioration of the moving parts and prevent full positive movement of the closure members.
Various non-mechanical means have been developed for the regulation of flow of particulate solids. U.S. Pat. No. 2,541,662 (Palmer, 1951) discloses a system in which air regulated by a conventional mechanical valve is used to accelerate or decelerate the flow of catalytic particles from a cracking reactor to a fractionator.
Regulated transfer of granular solids has also been provided by the use of a controlled pressure gradient across a seal leg. This mechanism is described in U.S. Pat. No. 4,078,675 (Woinsky; 1978) wherein the seal leg extends between vessels at different pressures and is provided with a plurality of gas conduits arranged to insure local pressurization at various points along the seal leg. The system is directed to affording uniform flow through the seal leg without creation of a fluidized condition.
Very recently, a system has been disclosed for regulated flow of particulate solids relying on a combination of carrier gas and metering gas. Solids discharging from a feed hopper are carried downstream by the carrier gas. The metering gas enters a plenum chamber in the system between the feed hopper and the carrier gas line to meter solids delivery to the carrier gas line. The system also includes a line to equalize the pressure above the solids in the feed hopper to the metering gas pressure in the plenum chamber. The system is described in Institute of Gas Technology Annual Report--June 1977, Project No. 8976.